Redheads have long been known to be at a higher risk for melanoma,
the deadliest type of skin cancer, because their fair and sometimes
freckly skin provides less natural protection against UV radiation from
the sun - or so doctors had thought.
New research shows that
genetic factors of the skin pigment that's predominantly found in
redheads may be what's to blame for the increased melanoma risk.
Melanoma
is the leading cause of death from skin disease, with more than 76,000
cases expected to be diagnosed in 2012 in addition to nearly 9,200
deaths caused by the cancer.
Fisher's study is published in the Oct 31 issue of Nature.
Human
skin contains different types of the pigment melanin, a natural
substance that gives the skin its color.
There's a dark brown/black form
called eumelanin which is predominantly found in those with dark hair
or skin, and also a lighter red/blond pigment called pheomelanin, which
is the predominant pigment in individuals with red hair, freckles and
fair skin.
According to the researchers, skin type alone can't explain the rise
in melanoma risk among redheads because this increased risk has also
seen been seen in skin areas not directly exposed to sun. They tested
that theory on two strains of mice that were genetically identical,
except one group was bred to have a gene that would give mice more
dark-colored pigment and the other group was bred to possess the
pigment-producing gene that causes red hair and fair skin in humans.
The
researchers used a method to activate a melanoma-causing gene that
typically requires UV radiation to create melanoma cancer cells in a lab
setting. However, they were surprised to find half of the red mice had
developed melanoma within months without UV exposure, compared with only
a few dark mice.
Next the researchers wanted to see whether the
red pigment itself may cause cancer, testing it on a group of "albino
redheads," which were fair-skinned mice who had their pigment production
genetically disabled. They found that by completely removing the
so-called "red-pigment pathway," the mice were completely protected
against melanoma.
The researchers say melanoma risk for redheads
might instead be caused by "oxidative damage," from molecules called
reactive oxygen species (ROS) which damage cells' DNA. The researchers
found higher levels of DNA damage caused by ROS in the skin of red mice,
but not in the albino redhead mice.
"Right now we're excited to
have a new clue to help better understand this mystery behind melanoma,
which we have always hoped could be a preventable disease," Fisher said.
"The risk for people with this skin type has not changed, but now we
know that blocking UV radiation - which continues to be essential - may
not be enough."
Since sunscreen may not offer full protection,
the researchers recommend that redheads be especially vigilant looking
for changes in their skin, and to never hesitate to get checked out by a
dermatologist.
"The big danger here is that somebody will say,
'Oh, well if I can't do anything about it, then I can go to a suntanning
salon and go tanning on the beach and just call it fate.' That's not
the case," Dr. Meenhard Herlyn, director of the Wistar Institute
Melanoma Research Center in Philadelphia, told The Los Angeles Times. "One still has to be very conscientious about not getting a sunburn and getting the damage."
Eugene Healy, a clinical dermatologist at the University of Southampton, U.K., however downplayed the findings to Nature News.
He said while the mechanism reported in the study is interesting, it is
probably a less common melanoma trigger than UV radiation. "You almost
never see melanoma, for example, on the buttocks," said Healy.
